This invention pertains to a device and method for dissipating the thermal energy dissipated by electronic circuit components, and more particularly the thermal energy associated with integrated circuit components located on printed circuit boards.
The problems associated with the release of thermal energy or heat generated by electronic circuit components is well known. A study by the U.S. Air Force reports that excessive temperature and resulting thermal overstressing accounts for fifty five percent of electronics failures. For further information about this study, the reader is referred to the web page http://www.flotherm.com/Prod.sub.-- Info/About.sub.-- FLOTHERM/about.sub.-- FLOTHERM.html#problem, the disclosure of which is hereby incorporated by reference.
Presently, electronic circuit components are installed on circuit boards and air is forced over the circuit elements to transfer the heat away from the component and circuit board. The movement of air is achieved by convection through the use of motorized fans. This mode of heat transfer is commonly referred to as forced air convection.
In addition, air movement heat transfer devices, such as heat sinks, are frequently used. A typical heat sink device 10 is shown in FIG. 1. The device 10 shown in FIG. 1 is attached to an electronic circuit component 20. Alternatively, the device 10 is connected directly to a circuit board (not shown). The device 10 typically includes heat transfer enhancing fins 30 that are added to increase the surface area of the device 10 the properties of the device 10. The device 10 is connected to the electronic circuit component 20 at an interface 40 and secured by adhesive or mechanical hold downs.
Some of the problems associated with existing with heat sink devices such as the device 10 shown in FIG. 1 are as follows:
a. The existing heat sink devices are generally expensive, especially when the device includes intricate brazed multiple thin fin construction to provide a large surface area for heat dissipation. PA1 b. The existing heat sink devices require a connection to the electronic circuit component, as they are not integral. Typically, adhesive is used to connect the heat sink to the circuit component. Since the principle of operation of existing heat sinks relies on conductive transfer from the component to the heat sink device, the adhesive connection has inherent shortcomings, such as increasing the thermal resistance between the heat generating source and the exposed surface area of the heat sink fins. PA1 c. Some circuit components, such as transformers and rheostats, are not easily connected to the heat sink devices. Alternatively, the heat sink devices are located on the circuit board apart from such circuit components. This arrangement is not ideal for heat dissipation. PA1 d. The size of the heat sink devices is proportional to the heat dissipated from the associated component. When the size of the heat sink device is large relative to the associated electronic circuit component the ability to access the component and its leads or even nearby components are inaccessible for testing and other operations. Furthermore, large heat sinks corrupt the airflow to upstream components. PA1 e. When the heat sink component can not be attached to the component due to size restrictions or the nature of the component, i.e. transformers and rheostats, locating the heat sink device alternatively at another location on the circuit board consumes valuable space on the circuit board. Increasingly, as technologies grow circuit board space is at a premium. PA1 f. The most efficient materials used to construct existing heat sink devices are expensive, such as copper or other highly conductive materials. The materials also add undesirable weight to the circuit board. PA1 g. A free air stream exists in the space above the circuit board. A number of factors determine the characteristics of the free air stream. In any event, existing heat sink devices frequently create an undesired obstruction to the free air stream aiding a degradation of the characteristics of the free air stream. For example, in addition to an obvious physical obstruction, the aerodynamic properties of the heat sink devices create eddies and vortices at the downwind side of the heat sink impeding the flow of the free air stream. PA1 h. When the fins of the existing heat sink devices extend well into the free steam of air, the heat transfer rate of thermal energy dissipated by components downstream of the heat sink is greatly reduced. PA1 i. Existing heat sink devices ideally require the largest contact surface interface to provide the most efficient heat transfer. This cannot be achieved when the component is an erasable programmable read only memory (EPROM) which does not permit a heat sink interface, due to the device design which enables reprogramming without replacing the device or other integrated circuit component that does not permit an efficient interface due to irregular surface area such as exposed electronic power modules. PA1 j. Heat dissipating components ordinarily have heat gradient characteristics. That is a specific location of the component is the principle source of heat dissipation. Existing heat sink devices do not provide a design that takes full advantage of this fact and thus do not attain the associated design, space and economic benefits.
The present invention is directed to overcoming, or at least reducing the affects of, one or more of the problems set forth above.